Printing telegraph system having serially connected, step-by-step automatically selective stations



Aprll 29, 1947. M. POTTS ET AL 2,419,730 PRINTING TELEGRAPH SYSTEMHAVING SERIALLY CONNECTED, STEP-BY-STEP AUTOMATICALLY SELECTIVE STATIONSFiled Feb. 28, 1944 INVENTORS LOUIS M. POTTS REGINALD G. SCHULERATTORNEY Patented Apr. 29, 1947 PRINTING TELEGRAPH SYSTEM HAVINGSERIALLY CONNECTED, STEP-BY-STEP AUTOMATECALLY SELECTIVE STATIONS LouisM. Potts, Evanston,

and Reginald G.

Schuler, Highland Park, 111., assignors to Teletype Corporation,Chicago, 111., a corporation of Delaware Application February 28, 1944,Serial No. 524,150

25 Claims.

This invention relates to telegraph switching systems and moreparticularly to such systems wherein the stations are included in asingle telegraph circuit and may be selected for telegraphiccommunication.

The principal object of the invention is to provide a system arranged topermit a central station operator to select rapidly and automaticallyany station of the system, establish telegraph communication with saidstation, and disestablish the connection following the telegraphiccommunication.

Another object of the invention is the provision of simple and enicientrelay selecting means at each of several remote stations responsive toconditions established by a central station operator for rendering theprinting telegraph equipment thereat operative with correspondingequipment at the central station.

A feature of the system resides in the provision of a plurality ofstation identifying keys which, when depressed, establish a conditionwhereby the station identified with such key will be selected andprepared automatically for telegraphic communication and will bemaintained for telegraphic communication pending further operation ofthe central station.

A further feature of the invention resides in the provision of a systemof station selection and telegraphic communication wherein stationselection and communication take place over one line conductor andmaintenance of the selection during the communication is assured byconditions established overa second or companion line conductor.

The above and other objects of the invention are attained by connectinga central station with a plurality of remotely situated stations bymeans of a pair of line conductors on one of which impulses determinedin accordance with the operation of a station identifying key aretransmitted, the number being determined by the operated station key,for operating apparatus at the remote station to connect and prepareautomatically the telegraph apparatus at such station for telegraphiccommunication. The other conductor of the pair of conductors extendingfrom the central station to the remote stations is utilized for thepurpose of maintaining the telegraphic connection established throughthe operation of the key identified with the desired station byestablishing a condition at the selected remote station whereby thetelegraphic connection cannot be disturbed except through a manualoperation by the central station operator.

Specifically, the objects of invention are accomplished by providing atthe central station a plurality of keys, one identified with each of theremote stations which are connected to the'central station bya pair ofline conductors extending from the central station to the remotestations and connecting said stations serially. Associated with the keysis a step-by-step switch mechanism responsive to the operation of any ofthe station keys for effecting transmission automatically of the numberof step-by-step stationselecting impulses required for the selection ofthe desired station, which are transmitted over one of the pair of lineconductors to the remote station desired for communication'where relaysare operated to open the line conductor. extending to the other stationslocated beyond the selected station and for preparing. a, condition-forthe connection to such line conductor of the printing telegraphapparatusat the selected re-' mote station. Following the establishmentof the identified condition the operator atthe central station operatesanother key to'connectthe printing telegraph apparatus at the centralsta tion with the line conductor and to operate another relay whichconnects through its contacts the printin telegraph apparatus individualthereto and located at the selected remote station. Maintenance of theestablished telegraphic communication between the central station andthe remote station is achieved by applying at the central station to theother conductor of the pair of .conductors a battery supply whichmaintains the several relays at the remote station energized during theperiod of telegraphic communication.

The central station operator may disestablish the previously establishedconnection with a remote station or select another station by operatingone of the several keys at the central station, which establishesconditions on the line circuit for the achievement of the desiredpurpose.

Any of the remote stations may signal the central station,.indicatingthat it desires to establish telegraphic communication with it. Thecentral station operator, upon observing the operation of the callingsignal, will establish a condition whereby the step-by-step impulsetransmitting selector at the central station will operate to transmit anumber of impulses required for theselection of the station identifiedwith the highest number of digital impulses. The number "of impulsesisdetermined by'the calling statlons position along the line conductor andthe controlling circuit pulses until it encounters an open ground at asubstation. If more than one station has signaled for a connection, the'central station will transmit the smallest number of impulses thatis'required to reach the nearfest substation. station under thesecircumstances, the operator proceeds with the telegraphic communicationin the manner previously outlined. a

The invention may be more fully understood from the followingdescription, when read in conjunction with the accompanying drawing,which shows a telegraph system embodying the features of the presentinvention.

Referring now to the drawing, there is disclosed a pair of lineconductors 5 and 6 extending from a central station I to a plurality ofremotely situated stations 8, 9, l3, and II. As disclosed, the lineconductors 5 and 6 connect the several stations 8, 9, l9, and Il inseries with the central station 1. While the drawing discloses but asinglepair of line conductors 5 and 6 extending from the central stationI, it is manifest that the system may include a plurality of other pairsof line conductors 5 and 5 extending from the central station 1 andconnecting therewith a plurality of different remotely situated stationsin the same manner as described above.

The apparatus at the central station 1 is included in the area withinthe broken lines. Likewise, the several remotely situated stations 8, 9,Land II are indicated by broken lines. However, only two of the remotestations have been shown complete, but it is, of course, understood thatremote stations 9 and I include apparatus identical with the apparatusdisclosed for stations8and (L.

Y At the central station there is a bank of keys l including a keyindividual to each of the remote stations which, when depressed,establishes a, condition for the transmission of the number of impulsesrequired for the selection of the remote station identified with thedepressed key.

Suchimpulses are generated through the operation of a step-by-stepselector switch 16 which includes two banks of contacts I! and I8 and astation indicator mechanism IS. A contactor in the: case of the banks ofcontacts I! and I8 and a pointer in the case f the station indicator [9are movable step by step in response to the operation of ,a steppingmagnet; that is, for each operation of the stepping magnet thecontactors and the pointer progress from their zero position step bystep to a position determined by the particular, key previouslydepressed. The impulses so generated are impressed on line conductor 5and traverse such line conductor to the several remote stationsprogressively, depending upon the number-of the desired station. At eachof the remote stations a single pair of counting relays is operated forestablishing conditions preparatory to the connection with the lineconductor of the printing telegraph apparatus at such remote station.The counting relay at any station merely advance the circuit or lineconductor to the nextstation, except when the called or calling stationis reached, when stepping will stop. When this position is reached,circuit conditions are established to apprise the central stationoperator that the station has been selected. The central stationoperator then operates a print key which disassociate-s from one of theline conductors the step-by-step impulse generating mechanism andconnects to such line conductor Following the selection of the N theprinting telegraph apparatus at the central station. Concurrently withthe connection of the printing telegraph apparatus at the centralstation with the line conductor the polarity of the battery applied tothe line conductor is changed, with the result that a relay is operatedat the selected remote station for opening the line circuit and forconnecting the printing telegraph apparatus at the remote station withthe line conductor. Also at the central station a condition isestablished whereby locking battery is applied to the other conductor ofthe pair of line conductors for maintaining the relays at the remotestation operated until the. operator at the central station operates aclear-out key or operates another station key.

Assume, for example, that the central station operator desires toestablish a connection with station I l, which may be designated by thenumber II, in which case the operator would depress key 2| of the bankof keys l5 after making certain that key 22 of such bank of keys is inthe call position or the position shown in the drawing. Of course, withthe key construction disclosed, when a station key is depressed, allother keys are released with the result that key 22 automaticallyassumes a calling position. With the depression of key 2| positivebattery is impressed on relay 24 and stepping magnet 25 over a circuitextending from grounded battery 26, conductor 21, swinger 28, andcontact 29 of key 21, conductor 30, winding of relay 24, conductor 3|,zero contact of bank of contacts l1, wiper 32, through a conductor 33,adjacent the shaft (not shown) on which the wipers 32 and 34 of the bankof contacts I! and I8 and the pointer 35 of the station indicator I9 aremounted, conductor 36, winding of stepping magnet 25, left-hand armatureand back contact of relay 31, left-hand armature and back contact ofrelay 38, and the winding of relay 39 to ground. Relay 24, steppingmagnet 25, and relay 39 will be energized over the circuit just traced.With the de-energization of the stepping magnet 25, the wipers 32 and 34and the pointer 35 will be advanced one step. With the energization ofrelay 39 the circuit of lamp 42 will be interrupted, which extendsnormally from grounded battery 26, conductor 43, right-hand armature andback contact of relay 39, conductor 44, and through the lamp 42 toground. Consequently, with the opening of the back contact of relay 39,the circuit of the lamp 42 will be interrupted and it thereby beingenergized and de-energized, the wipers 32 and 34 and the pointer 35 willbe advanced one step and then later step by step until the circuit,through the magnet 25, is opened. Relay 24, which may be energized onlywhen the wiper 32 of the bank of contacts I! is in its zero position,applies through its left-hand front contact and armature, ground to theleft-hand front contact of relay 39. Consequently, when relay 39 isenergized, an energizing circuit is established for relay 3! extendingfrom grounded battery 26, conductor 46, winding of relay 31, conductor41, extreme left-hand armature and back contact of relay 48,left-hand'armature and front contact of relay 39, left-hand armature andfront contact of relay 24 to ground. It is significant to note also thatrelay 24 in energizing opens at its left-hand back contact the circuitextending to line conductor 5 and also that with the energization ofrelay 3! the energizing circuit for the stepping magnet 25 is opened.With this operation the stepping magnet 25 will be 'de-energized.

As a result ofthe operations just described, the wiper 32 together withthe pointer 35 are moved to their second. position, in the case. ofwiper 32ito theposition corresponding to the key of the :bank: of keys lfor the remote station identified by the numeral I. Under suchcircumstances relays 24 and 39 will be de-energized. Relay $9 indeenergizing again closes the circuit for lamp 42. Also, with thede-energization of relay 39 the. energizing circuit for relay. 3Iisopened. When wiper 32 engages the first station contact .of the bankofcontacts I l the energizing circuit. for stepping magnet 25 and relay39 is again completed; with the consequent result. that lamp 42. will beextinguishedand relay 31' will be energized over a circuit extendingfrom grounded battery 26, conductor 16;- winding of relay 31, conductor4 extreme left hand armature and back contact of relay 48, left-handarmature and front contact of relay 39, left-hand armatureand backcontact of relay 2 t, conductor 5!, swinger'52 of key 22, line conductor5, normally closed contact 53 of relay 54, normally closed contact 55ofrelay 56, conductor 51, positive current rectifier 58,1eft-handwinding of relay 59; left-hand winding of relay 58, back. contact andleft-hand armature of relay til to ground. Relays 55 and 55am energizedover the circuit just traced in addition to the energization, of relay3? at the central station. With the venergization of relay 59,,theholding circuit for this relay isestablished through its right-handwindingv and front contact to the left-handarmature and front contact ofrelay 5%; Relay 55 in energizing, short-circuits ballast resistor 53 andestablishes through its right-handwindinga locking circuit extendingfrom ground at the last station over conductor 6" and through theseveralintermediate stations, right-hand back contact and armature of relay6!], conductor 64, right-hand winding oi relay 56, front contact andright-hand armature of relay 56, conductorBS, conductor 5, right-handback contact and armature of-relay 48, conductor 68, winding of relay6.? at the central station, conductor 553, to grounded battery 26. Relay59 will be released upon the energization of relay 39, since its holdingcircuit is broken at front contact of the left armatureof relay 3%.

The wiper 52 of the sequence switch I6 has completed another circuitfrom grounded battery through relays 39 and stepping magnet 25, contactNo. 2 of contacts and the left-hand normally. closed contacts of the No.2 key of the bank of keys I5. Steppingmagnet'25 and relay 59 operate aspreviously described. Likewise, relays at station No. 2'are energizedwhich are similar to. relays 59 and 55 at station No. 1, to complete thecircuit conditions previously dee scribed as being established atstation 8. This action is repeated until the wiper 32 of sequence switchit reaches segment No.11 of the bank of segments H, at which positionswinger 28. will be out of engagement with contact 10, whereupon theenergizing circuit for stepping magnet 25 and relay 39 will not becompleted. For such operation eleven impulses for the election of thestation will be transmitted. The Wiper 32 will, under suchcircumstances, not befurther advanced for such selection. Pointer 35will be opposite the segment numbered 11, which will indicate to thecentral station operator that stationll corresponding to key 2i has beenselected and has its circuits established preparatory to the connectionof the printing telegraph apparatus at suchstation with line conductor5.

It is significantto .note that; in connection awithr;

the energization and de:-energization cof'irelay 391 lampJl-Z will flashthus indicatingto the operator that switch lGiis .being .advanced' stepby step: to select the. desired station determined by: the. particularkey of the bank of keys-15:which hasbeen 1. operated However; whenlamp-Higlow contin-j uously, the operator isv apprised of thecompletion.

of the station selection.

Upon the observance .of the continuous glowof.

the lamp 42:. the operator; at the! central station. I depresses. thecall orprint key. 22rto open its:

left-hand. contact, thereby. opening the circuit extending throughconductor 5!, and closing at. its right-handcontacts two circuits- Onecircuitv completes the operating circuit for driving. motor 12.0f theprinting telegraph equipment l3.which.

includes a transmitter It and selector magnet 15 of a receivingprinterofanywell-known: come mercially available. type. The. othercircuitcompleted through the right-handcontactsuof. key. 22 extends fromnegative battery: 16. through the i normally closed-contactoftransmitterm, receiving. printer (windings of the selector magnetthereof), through thecontacts of key"2.2: to line conductor 5'extending. through the normally closed contact 5310f relay 5% at station8, the

contact of the relay correspondingto relay 54.

at stations 9. and IE, contact 19 of relay til at station, contact 81 ofrelay 82, negativecurrent rectifier as; andlright-hand winding. of relay8!] to ground. With regard .to the rectifiers as.-

sociated With each of the relays 59' and 83 .at.

stations 8' and H, respectively, it is; noted that the rectifier 53 or5-1 in circuit. with the left-hand windingof relays59land:83,respectively', is poled. to pass only currentofcpositivepolarity, Whereas-i the other rectifiers, namely 34 land 9!], are poledfor current of a negative polarity. Consequently,

relay 83 will respond only to current of apositiVe polarity and relayBfiwillrespond only to current of anegative polarity.

conductor 5 to conductor 85" which extendsto printing telegraphequipment 86, includingtransmitter 87 and receiving printer 88. It isnoted: that the left-hand winding of relay 8fl-is included in'thecircuit of line conductor 5 but the relay armature will not follow thesignals impressed on the line conductor 5 through the operation ofeither the transmitter 14 atthe central station! or the transmitter 81at station ll. Contact 19 of relay is also opened upon theenergizationof: such relay, thereby to open the line circuit 5 at suchpoint extending to the station beyond sta- I tion II and cause thedeenergization of relay 83.

Through the right-hand armature and front contact of relay 80 the powersupply for driving motor 89 of the printing telegraph equipment86iscompleted.

A driving-motor 12 of printing telegraph equipment 13 and the drivingmotor 89 of printing telegraph equipment 86 are now operating to supplypower to the respective equipment. The operator at the central station 1now operates the transmitter" to transmit a code combination of impulsesto cause operation of the receiving printer- 88 to select the functionbar allocated to thebell' signal. When such function bar operates, thebell associated with such printer operates tonotify the operator atstation I I that the central station desires to communicatetelegraphically. Toleraphic communication may now take place betweencentral station 1 and the remote station I I over the line conductor 5.It would, of course,

notbe necessary for the operator at the central station 1 to operate thebell signal of printer 88, for it is manifest that telegraphiccommunication might be commenced immediately upon the completion of theconnection between line conductor 5 and conductor 85 at station I I.Maintenance of the described connection is assured due to the holdingcurrent applied to the other conductor 6 which, together with lineconductor 5, constitute a pair of line conductors extending from thecentral station 1 to the station ll through the several intermediatestations such as 8, 9, and I0. Under locking conditions conductor 6extends through the locking winding of the relays corresponding to relay56 at each station.

When the communication between central station 1 and station II has beencompleted the operator at central station 1 may interrupt th establishedconnection either through the operation of clear-out key 92 of key bankl5 or the operation of another station key such as 93 thereof which maybe identified with station number 2 or station 9 of the circuitdisclosed in the drawing. The operation of either clear-out key 92 orkey 93 will cause through the movement of lock bar 94 of the key bank I5the restoration of previously depressed station key 2| and key 22.Through such operation the circuit for stepping magnet 25 will becompleted and the wipers 32 and 34, together with the pointer 19, willbe advanced step by step in the manner previously described inconnection with the selection of station II. This 'step-by-stepoperation will continue until wiper 32 reaches the contact identifiedwith key 93 or station 2, which in the disclosure is identified asstation 9.

Assume, for example, that instead of depressing key 93 the centralstation operator depressed clear-out key 92. The wipers 32 and 34 willbe advanced step by step until wiper 34 contacts segment 94, which isthe segment just prio to the zero segment or zero position of the wipers32 and 34. As the wipers 32 and 34 proceed to such position, all of thestepping relays at the several stations will be operated successivelyand all of the relays corresponding to relays 56 and 82 will beenergized andlocked up over a circuit including-line conductor 6. Whenwiper 34 engages segment 94, a circuit will be completed for theenergization of stepping magnet 25 and relays 39 and 48. Relay 48operates to open at its extreme left-hand armature line conductor 5 andto open at its'right-hand armature and back contact line conductor 5.Consequently, all of theenergized relays corresponding to relays 56 and82 at stations 8 and II will be de-energized. Relay 48, in energizing,also completes the circuit to the contacts of relay 95 and alsocompletes an energizing circuit for relay 38 which opens at its contact.

the energizing circuit for steppin magnet 25 and relay 39. With suchoperation the wipers 32 and 34 will be stepped an additional step or tothe zero position to await the operation of a key in the key bank I5.When any one of the individual station calling keys such as key 93 andclear-out key 92 are depressed, all other keys in the bank of keys arereleased and the last depressed key is locked down When key 22 is'depressed it is locked depressedbut does not release any other keysalthough it;is released through;

8 the depression of any of the other keys of the key bank.

If any one of the several outlying stations desires to communicatewiththe central station, the operator at the remote station depressesswitch 96 to establish an energizing circuit for relay 80, which'closes' through its left-hand armature and front contact a. holdingcircuit therefor, including signal lamp 9! which indicates to theoperator at such station that an attempt is being made to establish aconnection with the central station. Relay 68 in attracting itsleft-hand armature removes the ground from the windings oi relays 56 and59, with the result that these relays cannot, through the operation ofthe keys in the key bank I5, be energized. At the right-hand backcontact of relay 38, which is opened only momentarily, the lineconductor 6 is opened.

When line conductor 6 is momentarily opened at its back contact, relay6'! at the central station is de-energized, applying battery to thewinding of relay which is energized and which is locked up over acircuit extending from grounded battery 26, left-hand armature and backcontact of relay 99, inner right-hand armature and front contact ofrelay 95, winding of relay 95, to ground. Also, through thede-energization of relay 61, signal lamp 98 at the central station Iwill remain illuminated. Through the energization of relay 95, positivebattery is now applied to the zero contact of the bank of contacts Hwith the result that stepping magnet 25 and relays 24, 39, and 31 willbe energized. Under such circumstances the wipers 32 and 34 and thepointer 35 will be advanced one step in a manner previously described;that is, assuming that the wiper 32 was on its zero segment. However,should the wiper 32 not be on the zero segment and it is required torotate through the zero position to reach the selected station, thewipers 32 and 34 and the pointer 35 will be advanced step by step untilthe wiper 34 engages segment 94, to establish a circuit to relay 39,stepping magnet 25, and relay 48. Relay 48 will be energized, openingthe circuit of line conductor 6, as previously described, and connectingground through a contact of relay 95 to the winding of relay 99. Duringthe time relay 48 maintains its right-hand front contact closed, acircuit for maintaining relay 5'! energized is established. Relay 99will be energized and locked to ground through a contact of relay 24 andwill also open the lockin circuit of relay 95 and again place positivebattery from grounded battery 29 on the zero segment of the bank ofcontacts IT. AS relay 48 operated, it opened the circuit extending toline conductor 5, rendering the closure. of the line conductor at relay39 ineffective, and thus precluded the application of pulsing current toline conductor 5. Such a condition prevents any false stepping oi' thestepping relays at any of the outlying stations. With positive batterynow connected to the zero segment of the bank of segments H, the wipers32 and 34 and the pointer 35 will be advanced step by step through theenergization and de-energization of stepping magnet 25 until wiper 32engages an open segment corresponding to the station at which key 98 hasbeen operated. When this occurs, lamp 42 will glow continuously and theoperator at central station I will be apprised of the selection of thestation desiring to communicate with the central station. Thecentral-station operator will now de press key 22 to-complete thecommunication-circuit, start the motor 52 of the printing telegraphequipment 13, and energize relay 54 to connect its associated printingtelegraph equipment me with line conductor in a manner previouslydescribed for the selection of station Upon the de-energization of relayE l-during the period wiper 32 is moving from itszero to its No. 1contact, the locking circuit of relay 99 is opened, whereupon this relayis released. Relays 95 and 99 will remain de-energized until asubsequent break signal is received from one of the remote stations,when the cycle of operation previously described will be repeated.,Of-course, with the de-energization of relays 95 and 99 and the closureof line conductor 5 through the righthand armature and back contact ofrelay 48, relay 6'! is again energized and remains in the position shownin the drawing until the line circuit, due to the energization of relay60 at station 8 or the relay corresponding thereto at the otherstations, is energized.

While the invention has been disclosed and described as applied toparticular circuits and apparatus, it is manifest that modifications arepossible without departing from the spirit and scope of the invention.

What is claimed is:

1. In a telegraph system, a central station, a plurality of substations,a line conductor extending from said central station to said pluralityof substations and serially connecting said central station with saidsubstations, printing telegraph apparatus at each of said stations, asingle series of counting relays with a singleunit of said relays ateach substation, means at the central station for generating a series ofstepby-step impulses to operate the units of said relays successivelycomprisinga plurality of segments, a contactor engaging said segments,means for advancing said contactor step-by-step to generate step-by-stepimpulses, and means identified with a called substation for controllingthe degree of operation of said contactor whereby relays at saidsubstations will be operated to prepare for telegraphic communicationover said line conductor by said telegraphic apparatus.

2. In a telegraph system, a central station, a plurality of substations,a line conductor extending from said central station to said pluralityof substations and serially connecting saidcentral station with saidsubstations, printing telegraph apparatus at each of said stations, asingle series of counting relays with a single unit of said relays ateach substation, means at the central station for generating a seriesofstep-by-step impulses to operate the units of said relays successivelycomprising a plurality of segments, a contactor engaging said segments,means for advancing said contactor step-by-step to generate stepby-stepimpulses, means identified with a called substation for controlling thedegree of operation of said contactor whereby relays at said substationsWill be operated to prepare for telegraphic communication, and means forconnecting said telegraphic apparatus with said line conductor followingthe arrestment of the contactor.

3. In a telegraph system, a central station, a plurality of substations,a line conductorv extending from said central station to said pluralityof substations and serially connecting said central station with saidsubstations, printing telegraph apparatus at each of said stations, asingle series of counting relays with a-single unitof said relays ..ateach substation, mean at the central station for generating a series of.step-by-step impulses to operate the units of said relays successivelycomprising a plurality of segments, a contactor engaging said segments,.an electromagnetic means for advancing said contactor step .by. step,to

generate step-.by-stepimpulses, means, identified witha calledsubstationfor controlling'thedegree of operation of said contactor whereby relaysat said substations will be operated to prepare for telegraphiccommunication, and meansat the called substation responsive to acondition .established at the central station for connecting thesubstation printing telegraphapparatusto the line conductor.

4. In a telegraph system, a centralstation, a plurality of substations,a line conductor extending from-said central station to said pluralityof substations and serially connecting .said central-station Withsaidsubstations, printing telegraph apparatus at each of said stations, .asingle series of counting relays with a single unit of said relays ateach substation, meansat the central station for generating a series,oflstepby-step impulses to operate the units of .said relayssuccessively comprising a plurality of 56%- ments, a contactor engagingsaid segments, means for advancing said contactor step-,by-step togenerate step-by-step impulses, means identified with a calledsubstation for controllingthe degree of rotation of said contactorwhereby relays at said substations will be operated to prepare fortelegraphic communication, and i .a relay at the called substationresponsive to ,a condition-established at the'central station. forconnecting the substation printin telegraph apparatus to the lineconductor.

,5. In a telegraph'system, a central station, a line conductor extendingfrom said centralstation to a plurality-of substations and seriallyconnecting said central station with said substations, printing'telegraph apparatus at :each of said stations,a single series ofcountingrelays with a single unit of said relays at each substation,means at the central station. for-generating in a step-by-step mannersubstation selection impulses of a predetermined character to operatethe units of said relays successively, means at the substationsresponsive to said-stepby-step selection impulses for conditioning itsprinting telegraph apparatus for connection with said line conuctor, andmeans at the selected substation in response to a superaddediimpulse ofa different character from the station selection impulses for connectingthe substation printing telegraph apparatus to the ,line iconductor.

6. In a telegraph system, a central station, a line conductor extendingfrom said central-station to a plurality of substations and seriallyconnecting said central station with said substations, printingtelegraph apparatus at each of said stations, a singleseries ofcounting, relays with a single unit of said relays at each substation,means at the central station for generating in a step-by-step -mannersubstation selection impulses of a predetermined character to operatethe unitsof said relays successively, means at the substationsresponsive to said stepby-step selection impulses for conditioning itsprinting telegraph apparatus for connection with said line conductor,and a relay at the selected substation responsive to a superaddedcurrent impulse of a character different from the imi V 11 c pulseswhich effected ,the selection of the substation for connecting thesubstation printing telegraph apparatus to the lin conductor.

.7. In ,a printing telegraph system, a central station, a plurality ofremote substations, a line selectively with any of said substations andfor terminating the line conductor at the selected substation, and meansat the substation responstations, means at the central station forestab- ,lishing printing telegraph control conditions .sive to acondition difierent than the condition 7 which effected its selectionfor connecting the printing telegraph apparatus thereat with the lineconductor.

8. In a printing telegraph system, a central conductor extending fromsaid central station and connecting said substations in seriestherewith, printing telegraph apparatus at each of said stations, meansat the central station for establishing printing telegraph controlconditions selectively with any of said substations and for terminatingthe line conductor at the selected substation, a second line conductorextending from said central station to each of said substations, andmeans operative over said second 'line conductor for maintaining theoperative connection of the printing telegraph apparatus at thesubstation with said other line conductor.

9. In a printing telegraph system, a central station; a plurality ofremote substations, a line conductor extending from said central stationand connecting said substations in series therewith, means at saidcentral station for establishing printing telegraph control conditionsselectively with any ofsaid substations and for terminating the lineconductor at the selected substation, means at said substationsoperative in response to conditions generated at the central station forextending the line conductor stepgraphic conditions selectively with anyof said substations and for terminating the line conductor at theselected substation, means at said substations operative to conditionsgenerated at the central station for extendin the line conductor step bystep from substation to substation until the called substation isselected, means at the central station for indicating to the operatorthereat when the called station has been selected, and means operatedfollowing the selection of the called substation for connecting theprinting telegraph apparatus thereat with the line conductor.

11. In a telegraph system, a central station, a plurality of remotesubstations, a line conductor extending from said central station andconnecting said substations in series therewith, printing telegraphapparatus at each of said substations, means at said central station forestablishing telegraphic conditions selectively with any of saidstation, a plurality of remote substations, a line I,

substations and for terminating the line conductor at the selectedsubstation, means at said sub- 'stationsoperative to conditionsgenerated at the central station for extending the line conductor stepby' step from substation to substation until the called substation isselected, means at the central station for indicating to the operatorthereat the process of establishing a connection and when the calledstation has been selected, and means operated by a condition differentfrom the station selecting conditions following the selection of thecalled substation forconnecting the printing telegraph apparatus thereatwith the line conductor.

12. In a telegraph system, a central station, a

plurality of remote substations, a line conductor extending from saidcentral station and connecting said substations in series therewith,printing telegraph apparatus at each of said substations, a singleseries of counting relays with a single unit of said relays at eachsubstation, means at the central station for generating a series ofstepby-step impulses to operate the units of said relays successivelycomprising a plurality of segments, a contactor engagin said segmentsfor generating impulses to said line conductor, means for advancing saidcontactor step by step, a key identified with each of the substations,and means operative under the control of an operated key for determiningthe degree of rotation of said contactor and for terminating theimpulses impressed on said line conductor whereby the relays at thesubstation identified with the operated key will be operated to preparefor telegraphic communication over said line conductor by saidtelegraphic apparatus.

13. In a printing telegraph system, a central station, a plurality ofremote substations, a line conductor extending from said central stationand connecting said substations in series therewith, printing telegraphapparatus at each station, means at said central station forestablishing printingtelegraph control conditions selectively with anyof said substations and for terminating the line conductor at theselected substation, means at said substations operative in response toconditions generated at the central station for extending the lineconductor step 'by step from substation to substation until the calledsubstation is selected, and means at each of said substations forterminating the line conductor thereat when a connection with thecentral station is desired and for establishing conditions whereby themeans at said central station will be operated automatically to select acalling station.

' ,14. In a telegraph system, a central station, a

plurality of remote substations, a line conductor extending from saidcentral station and connecting said substations in series therewith,printing telegraph apparatus at each of said substations, means at saidcentral station for generating stepby-step impulses of a predeterminedpolarity, means at said substations operative in response to saidstep-by-step impulses for extending the line conductor step by step fromsubstation to substation until the called substation is selected, andmeans at the selected substation responsive to an impulse of a polaritydifferent from the step-bystep impulses for connecting the printingtelegraph apparatus thereat with said line conductor.

15.In a telegraph system, a central station, a plurality of remotesubstations, a line conductor extending from said central station andconnecting said substations in series therewith, printing telegraphapparatus at each of said substations,

means at said central station for generating stepby-step impulses of apredetermined polarity, means at said substations operative in responsearm-mo to --said-step-'by st'ep impulsesior extending the line conductorstep by step 'from substation to substation until the called substationis selected,

'and a relay at theselected station responsive to a current impulse of apolarity different irom'the polarity of the step-by-step impulses forconnecting the printing telegraph apparatus thereat with the lineconductor.

16. In a telegraph system, a central station, a

plurality of remote substations, a line conductor by-step impulses of apredetermined=polarity,= means at'said substations operative in responseto said step-by-step impulses for extending the line conductor step bystep from substation to substation until the called substation isselected, and a relay at the selected station responsive to a currentimpulse of a polarity different from the polarity of thestep-by stepimpulses for cOnnecting the printing telegraphapparatus thereat with theline conductor and for terminating said line conductor at the selectedsubstation.

17. In {telegraph system, a'central station, a plurality of remotesubstations, a line conductor extending from said centralstation andconnecting said. substationslin. series therewith, printing telegraph.apparatus. at .each 1 of said substations, means at said central stationfor generating stepby-step impulses of a predetermined polarity, meansat said substations operative in response to said step-by-step impulsesfor extending the line conductor step by step from substation tosubstation until the called substation is selected, a relay at theselected station responsive to 2, current impulse of a polaritydifferent from the polarity of the step-by-step impulses for connectingthe printing telegraph apparatus thereat with the line conductor, asecond line conductor extending from said central station and connectingsaid substations in series therewith, and means operated over saidsecond line conductor for maintaining the connection established throughthe operation of said relay with said other line conductor.

18. In a printing telegraph system, a central station, a plurality ofremote substations, a line conductor extending from said central stationand connecting said substations in series therewith, printing telegraphapparatus at the central station, printing telegraph apparatus at eachof the substations, a single series of counting relays with a singleunit of said counting relays located at each remote station, means atthe central station to generate a variable number of stepping impulsesover said line conductor to operate the relay units at the differentsubstations in succession, means identified with each substation, meansoperated through the actuation of the means identified with thesubstation for initiating the operation of said impulse generatingmeans, and means controlled by said relay unit for connecting theprinting telegraph apparatus at the substation with the line conductor.

19. In a printing telegraph system, a central station, a plurality ofremote substations, a line conductor extending from said central stationand connecting said substations in serie therewith, printing telegraphapparatus at the central station, printing telegraph apparatus at eachof the substations, a single series of counting relays with a singleunit of said counting relays located at each remote station, means atthe central station to generate a variable number p of stepping impulsesover said line conductor tooperate the relay units at the diflerentsubstations in suc 'cession, means identified with each substation,means operated through the actuation'of the means identified with thesubstation for initiating the operation of said impulse generatingmeans, -means controlled by said relay unit for connecting the printingtelegraph apparatus at thesubstation with the line conductor, andmeansfor discontinuing the'operation ofsaid impulse-generating means when thecalled-station has'been selected.

20. In a printing "telegraph system, acen-tral station, a plurality ofremote substations, a 'line conductor extending from said centralstation and connecting said substations in series therewith, printingtelegraph apparatus at the central 'station,; printingtelegraphapparatus at each of the substations, a" single series ofcountingrelays with a singleunit of said counting relays located at eachremote statiommeans at the central :st-ation to generate afvariablenumber of stepping impulses over said line'c'onductor to operate'therelay units at the difierent substations inssuccession, a key identifiedwith. each substation, means operated through the actuation of the' keyidentified: with the substation for initiating the operationiof saidimpulsegenerating means, means for discontinuing'theoperation'of saidimpulse generating means when the called station has been selected asdetermined by the actuated key, and means controlled by the relay unitfor connecting the printing telegraph apparatus at the substation withthe line conductor.

21. In a printing telegraph system, a central station, a plurality ofremote stations, a line conductor extending from said central station inseries through said remote stations, printing telegraph apparatus ateach station, automatic means at the central station to condition theline conductor from the central station to any of the remote stationsfor telegraphic communication, a calling key at each remote station toinitiate the operation of said automatic means at the central station inresponse to the depression of any of said calling keys, means at thecentral station to indicate the station to which the line conductor isconditioned in response to the operated calling key, and means toconnect the printing telegraph apparatus at the central station and theprinting telegraph apparatus at the connected remote sta' tionsimultaneously to the line conductor and to initiate their operation.

22. In a telegraph system, a central station, a plurality of remotestations, a line conductor extending from said central station andconnecting said remote stations in series therewith, automatic controlmeans comprising a counting chain with a single unit of said chain ateach station to connect the central station to any one of the remotestations, telegraph apparatusat each of the stations, means to connectsimultaneously the telegraph apparatus at the central station and at theselected station with the line conductor, and automatic means toinitiate the operation of said automatic control means in response tothe disconnection of the telegraph apparatus from the line conductor.

23. In a printing telegraph system, a central station, a plurality ofremote stations, a line conductor extending from said central stationand connecting said remote stations thereto, printing telegraphapparatus at each station, a calling key at each remote station,automatic step-by-step L15 selector switch control means at the centralstation to connect the central station to any selected station, means toinitiate the stepping of said automatic switch control means in responseto the depression of any of said keys, and means to connect the printingtelegraph apparatus at the central station and the printing telegraphappa- -ratus at the connected remote station simultaneously to the lineconductor and to initiate their operation.

24. In a printing telegraph system, a central station, a plurality ofremote stations, a line conductor extending from said central stationand connecting said remote stations thereto, printing telegraphapparatus at each station, a calling key,

at each remote station, automatic step-by-step selector switch controlmeans at the central station to connect the central station to anyselected station, means to initiate the stepping of said automaticswitch control means in response to necting said remote stations withsaidcentral station, a single seriesof counting relays witha single unitof said relays at each substation, switch control means at the centralstation efiective through said counting relays to connect any of theremote stations to the line conductor, telegraph apparatus at eachstation, means to register calls at a plurality of stationssimultaneously, means at the central station responsive to saidregistration to initiate the operation of said switch control means,means to connect the telegraph apparatus to the line conductor inresponse to the establishment of a condition at any one of the callingstations, and means responsive to the disconnection of the telegraphapparatus from the line conductor to initiate again the operation of theswitch control means at the central station.

LOUIS M. POT'IS.

REGINALD G. SCHULER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,260,711 Hallden Oct. 28, 19411,059,706 Brodton Apr. 22, 1913 2,269,692 Rosene Jan. 13, 1942

